Quantitative Mass Spectrometry incorporates collaborative projects in which the Mass Spectrometry Group provides quantitative information about, typically, small molecules by GC/MS, LC/MS and LC/MS/MS or a combination. An example of the types of projects this includes is the isoprostane analyses undertaken as part of the NIEHS led study of biomarkers of oxidative stress. We currently have three major collaborations underway: 1) with Darryl Zeldin on Atherosclerosis Risk In Communities (ARIC) Ancillary Study; 2) with James Mohler on Interference with the Androgen Receptor and its Ligands in Recurrent Prostate Cancer; and 3) with Ron Cannon on fatty acid profile differences in a mutant mouse strain compared to wild type.